Electrocatalytic Studies of Group VI Metals

Abstract

Formate is one of the only economically viable products from CO₂ reduction due to its industrial versatility and excellent compatibility with current liquid-based fuel infrastructure. Here we report group 6 electro catalysts that selectively reduce CO₂ to formate with high faradaic efficiencies, 93+-5%. This class of catalysts are based on the structure of M(a-diimine)(CO)4, where M=Cr, Mo, and W. However, their mechanism is not clearly understood. We hypothesize a proton-tautomerization occurs from the ligand to the metal center, generating a metal-hydride with sufficient hydricity to reduce CO₂ to formate. Therefore, understanding the effects of metal basicity and ligand conjugation will aid in catalyst design of group 6 metal complexes for optimized proton-coupled reduction processes. NMR and EPR characterization will allow for direct observation of metal-hydride species. Assuming a metal-hydride is observed, further studies with NMR or UV-vis will estimate hydricity values.